1. Field of the Invention
The present invention generally relates to aiming sights for use with firearms and, more particularly, to a fused thermal and a direct view aiming sight.
2. Background Art
Conventional aiming sights superimpose an aiming reticle on the view of a target scene for the use of firearms during the day-time. For the use of guns, such conventional aiming sights include non-magnified (1×) aiming sights such as a reflex (red-dot) aiming sight as taught in U.S. Pat. No. 3,905,708; and also include holographic aiming sights as taught in U.S. Pat. Nos. 5,483,362 and 6,490,060. For the use of rifles, such conventional aiming sights include magnified aiming sights such as a rifle scope.
Conventional aiming sights for night-time use of firearms typically include a thermal imager, an image intensified night vision tube, or a low-light CCD sensor. The target scenes provided by these night-time use aiming sights are displayed on a screen together with an electronically generated reticle.
A visible imaging sensor such as a CCD sensor or an image intensifier tube provides high image resolution and a familiar view (i.e., visible/near IR electronic image) of the target. However, a well-camouflaged target can be difficult for the CCD sensor to detect because camouflages are designed to blend into the background in the visible to near infrared (400 nm to 900 nm) spectral region. A thermal imager operating in the LWIR (8 μm to 12 μm) spectral range can detect warm well-camouflaged bodies such as human beings. However, target identification (e.g., friend or foe) with a thermal imager is difficult. The thermal imager provides a thermal electronic image or map of the target at modest resolution which is quite unlike the familiar visible image. Attempts have been made to combine a CCD sensor and a thermal imager in order to fuse the visible/near IR and thermal electronic images in order to combine the strengths of the CCD sensor and the thermal imager.
CCD video sensors and image displays have limited resolution and dynamic range. The amount of information conveyed is a fraction of the information provided by the human eye. Moreover, target aiming by looking at a display screen is indirect and relatively slower than by looking through a conventional aiming sight. This is particularly true in close quarter battles where a 1× electronic sight such as a holographic aiming sight or a red-dot aiming sight allows an operator to keep both eyes open and focused at the target scene.